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J Clin Epidemiol. 2005 Aug;58(8):859-62.

Sample size calculation should be performed for design accuracy in diagnostic test studies.

Author information

1
Unité de biostatistique et d'Informatique médicale, Hôpital Tenon, Paris, France. flahault.a@wanadoo.fr

Abstract

BACKGROUND AND OBJECTIVES:

Guidelines for conducting studies and reading medical literature on diagnostic tests have been published: Requirements for the selection of cases and controls, and for ensuring a correct reference standard are now clarified. Our objective was to provide tables for sample size determination in this context.

STUDY DESIGN AND SETTING:

In the usual situation, where the prevalence Prev of the disease of interest is <0.50, one first determines the minimal number Ncases of cases required to ensure a given precision of the sensitivity estimate. Computations are based on the binomial distribution, for user-specified type I and type II error levels. The minimal number N(controls) of controls is then derived so as to allow for representativeness of the study population, according to Ncontrols=Ncases [(1-Prev)/Prev].

RESULTS:

Tables give the values of Ncases corresponding to expected sensitivities from 0.60 to 0.99, acceptable lower 95% confidence limits from 0.50 to 0.98, and 5% probability of the estimated lower confidence limit being lower than the acceptable level.

CONCLUSION:

When designing diagnostic test studies, sample size calculations should be performed in order to guarantee the design accuracy.

PMID:
16018921
DOI:
10.1016/j.jclinepi.2004.12.009
[Indexed for MEDLINE]

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